Nitroform inhibited fuels



2,847,292 NITROFORM INHIBITED FUELS Karl F. Hager, Clear-field, Pa., and Morris Rosenthal, Sherman Oaks, Calif.; said Hager assignor to the United States of America as represented by the Secretary of the Army No Drawing. Application October 16, 1956 Serial No. 616,354

14 Claims. (Cl. 52-.5) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described hereinmay be manufactured and used by or for the Government for governmental purposes without the payment of any royalties "thereon. The present application is a continuation-in-part of our co-pending application, Serial No. 228,771, filed.

May 28, abandoned.

This invention relates :to the protection of metals against corrosion.- I

Today aqueous solutions :of alcohols, ketones and other water-soluble organic compounds are being utilized as propellants for rocket and other metallic internal combustion engines. Such propellants are well known to have a corrosive effect on iron and more particularly upon magnesium and other light metals. It is accordingly the main object of the invention to provide means for the protection of such metals from the corrosive action of propellant fuels and especially from the action of propellant fuels. containing water. v

To carry out the objectsof this invention, the inventors have discovered that .the addition of small amounts of nitroform or its salts to aqueous solutions of watersoluble organic fuels inhibits corrosive attack against metals. Nitroform is a colorless water-soluble explosive compound with a melting-point of 150 C. and the formula CI-I(NO Where this compound or one of its potassium salts is utilized, iron or steel containers are protected against corrosion from the aforementioned propellants. Magnesium containers, important in aviation and rocketry where weight must be kept to, a mini mum, are also protected and may be used with the aqueous propellants.

Illustrative of the practice of the present invention, the following examples are given:

1951. The latter application has become Example 1 Tests of the corrosion inhibition of nitroform were made by subjecting strips of mild steel about 40 cm. in area to inhibited and uninhibited water solutions of 75% ethanol contained in stoppered tubes at ambient temperatures. Similar tests were made by subjecting strips of mild steel about 40 cm. in area to inhibited and uninhibited water solutions of 50% acetone contained in stoppered tubes at ambient temperatures. The Water-soluble organic compounds were inhibited with 0.05% of nitroform in different test tubes.

The mild steel pieces in the uninhibited fuels started rusting the first day and corroded more and more as time went on. The pieces in the inhibited fuels exhibited no corrosive effects for several months but after six months did show a few rust spots. Even after six months the surfaces remained 95% rustfree. By this time however the steel pieces in the uninhibited fuels were 100% covered by a thick layer of corroded metal and there was a heavy rust deposit at the bottom of each test tube.

2,847,292 Patented Aug. 12, 1958 2 Example 2 The tests of Example 1 were repeated except for the substitution of magnesium strips for the steel strips. I

The uninhibited fuels immediately showed an evolution of hydrogen bubbles caused by the corrosive attack on the magnesium. The inhibited fuels showed no trace of gas evolution while the magnesium in these fuels gave no evidence of corrosive attack. Within one month a white deposit of magnesium hydroxide had appeared in the bottoms of the test tubes containing the. uninhibited fuels. No such precipitate was present in the test tubes containing the nitroform inhibited fuels..

The surfaces of the magnesium in the uninhibited fuels had become totally encrusted with white crystals within six months. After six months magnesium in the inhibited fuels exhibited only a thin white crystalline .deposit over a very smal larea. Excellent corrosion inhibition was obtained from the nitroform.

Example 3 Samples of:mild steel and magnesium were cut to give a surface area of approximately 37 cm. and were ground to a smooth surface. After degreasing, the samples were placed in individual test tubes and partially submerged in a water solution containing 75 ethanol. The potassium salt of nitroform was added to some of the test tubes 'of alcohol-water mixture in concentrations of 0.1% and 0.05% by weight. At the end of three days the samples were examined and the steel specimens placed inthe alcohol-water mixture to which no inhibitor had been added had rust spots below and above the liquid-vapor interface. The magnesium specimens in the uninhibited alcohol had large discolored areas indicating corrosion in the liquid portion of the system although'the portion in the vapor seemed not to be affected. Thespecimens of steel and magnesium in the alcohol-water mixture inhibited by the potassium salt of nitroform showed very little, if any, corrosion. It should be noted that the inventors do not Wish to be sium salt or salts while in solution.

E p e .4

Samples of steel and magnesium Werecut, conditioned, and tested in the same manner as in Example 3. However, the samples were partially emerged ina water solution containing 50% acetone. The potassium salt of nitroform was added in concentrations of 0.1% and 0.05% by weight. In a three day period discolored spots were evident on the steel and magnesium samples in the uninhibited fuel. The steel and magnesium samples which were in the acetone-water mixture inhibited with .l% and 0.05% potassium salt showed very little, if any, corrosion.

We claim:

1. A liquid fuel mixture consisting essentially. of a major amount of an aqueous solution of a water soluble organic compound of the class consisting of alcohols and ketones and a minor amount of an inhibitor of the class consisting of nitroform and the potassium salts of nitroform sufiicient to inhibit corrosion of metal surfaces.

2. A liquid fuel consisting essentially of a mixture of water and an organic compound of the class consisting of water soluble alcohols and ketones and a minor amount of nitroform suflicient to inhibit corrosion of metal surfaces.

3. A liquid fuel consisting essentially of a mixture of water and an organic compound of'the class consisting of water soluble alcohols and ketones and a minorv amount,

of t e pa s m sa t 9 nitroformu ut c e t inhibit corrosion of metal surfaces.

4. The method of protecting metal surfaces of the class consisting of iron, steel angl magnesium from the corrosive action produced by liquidfuel mixtures consisting' essentially ofw atelrtand g,w; ;'rf 61p51"jo g compound of tl'ieclass consisting of alcohols a cl b V incontact therewith, yv ch 'c'fonipi ises acting said fuel mixture with tlie metal surfacein the pr ence of small amount of ah inhibitoriof the class consisting of nitroforrn and the potassium salts o f nitroforrn sufljcient toinhibit cQrros ioiiQand thereby treating s faces to produce 1 a armband inhibi ng actionI.tl g er eon whereby 'said surfaces are frendiere sulis'tanti all y inactive with respect to theno'r'rna l act on of said fuel mixtures; A t

-5.' The method of protecting rnetal surfaces of the class consisting bench; steel and. magnesium the corrosive action produced by fuel" mixtures consisting essentiallybfiwater and a water soluble organic compound of the class consisting" of alcohols and ilgeiton es in contact therewith; which comprises contacting s aid fuel mixture with the metal surface in the presence of a small amount of nitroforrn suflicient to inhibit corrosion, and thereby treating said metal surfaces to produce a corrosion .inhibiting actionlthereon whereby said surfaces are rendered substantially inactive with respect to thenormal corrosive action ofsaid fuel mixtures:

6. The method .of protecting metal surfaces of the class .consisting of iron, .steel and magnesium from the corrosive action produced by liquid fuelmixtures consisting essentially .ofwater and .a Water soluble organic compound of the class consisting of alcohols and ketones in contact therewith, which comprises contacting said fuel mixture vwith..the metal surfacelinthe presence of a small .amount of .the potassium salts of nitroform suffici'ent ,to inhibit corrosion, and thereby treating said metal surfaces to produce a corrosion inhibiting action thereon .whereby said surfaces are rendered substantially inactive with respect ;to the normal .corrosive action of said fuel mixtures.

7. A liquid fuel consisting essentially of 75% ethanol, and water, to which has "been added approximately 0.05% nitroform as a corrosion inhibiting agent.

8. A liquid fuel consisting essentially of 75% ethanol, and water, to which has been from between 0.05% to 0.1% of the potassiumsalts of nitroform as a corrosion inhibiting agent.

9. A liquid fuel consisting essentially of 50% acetone,

and WMQI, li v which ha been added approximately 0.05% nitroform as a corrosion inhibiting agent.

10. A liquid fuel consisting essentially of 50% acetone, and water, to which has been added from between 0.05% to 0.1% of the potassium salts of nitroform as a iahilzit a e qq 11. The method of'protecting metal surfaces of the las snsi i s r n st e and tlpa nq ium t pm the a sati e a n retest 1 b liquid i ss so is i e s n l y o 15% ethano and twat mwhi consists in adding to said fuel mixtures about .;0.05.% nitroform d hereb reatin meta with said nitroform as an agent to produce a corrosion inhibiting action on said metal surfaces, whereby said surfaces are rendered substantially inactive with respect to th Qrrna Q rq x n qf seis fue 1-2. The method of protecting metal surfaces of the class on t of i s s e aadtmasnssium item-t wr fib a qs i ssl .bY'. iq r f e were cansistinghess'entially of %ethanol, 5119' water, which consists in addihg Ito said fuel ri' ixture 'frcm between 0 1% t ta amsat w thereby treating said metal surfaces with potassium salts-of nitroform-as'an agent to produce'a ,c resign inhibiting action on said me t al nrface wh m surfaces are r e ncleredsubstantially inact: g to h normal c r e act o ofisaid f e imme 13; h v fl P greeting meta si taees :of the class csfisistiilg f ir n tan e asnss am rsnn the corrosive :acjtion produced by a li guid ifgel ur e sr il e en a .6 0 s tors? nd Wa er which q l Fl i9 3 5 9 ,950? 9 1. nitroform, and thereby tre ngisaidn etal s aces with said-fiitf6fdftii a as??? t6 Pro u s satiat on b ib t g' ast qa 1 sa s ei t sw essstu bysasi HI- facs are'rendered substantially inactive th respect to the normal corrosive: actioniof said fuel mixture;

"1495116 method q 'iinbfi t ih n t atfaq o the as l as tiii l l imp; stee d ,ax sn sium 29.!!! t e or s M91 rance y iau s fi raira sonsisting essentially of 50% acetone, and water, which s s n as fli t said fue .a z yx between 0.015%10 0 1% bfittre potassiurn'salts of nitroform, and r i sat r $9. 21 sisa 5 9 -,W 1 aid. ne Siam salts ii hit fi r a a a a to .p quse qnas sm inhibiting a i 92 a d inst? situates. w reb aid t ve= w ies c d is sai ts! Qr P Y a t on q aid fue slive s No references cited. 

1. A LIQUID FUEL MIXTURE CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF AN AQUEOUS SOLUTION OF A WATER SOLUBLE ORGANIC COMPOUND OF THE CLASS CONSISTING OF ALCOHOLS AND KETONES AND A MINOR AMOUNT OF AN INHIBITOR OF THE CLASS CONSISTING OF NITROFORM AND THE POTASSIUM SALTS OF NITROFORM SUFFICIENT TO INHIBIT CORROSION OF METAL SURFACES. 